This Issue focuses on a research article by Stohlgren et al. (2003) and two responses to it that were published in Frontiers in Ecology and the Environment. The article discusses the ecology of invasive species and the vulnerability of high diversity communities to invasives. Students, like many others, might assume that habitats with low plant diversity are more vulnerable to invasions of non-native plants than ones with high plant diversity. In contrast, Stohlgren et al.’s (2003) data show just the opposite. These data, plus subsequent comments and data in the “Write Back” section of Frontiers, allow students to explore questions about possible relationships between diversity of native species and a community’s vulnerability to non-natives, effects of scale on the correlation of native and non-native plant diversity, and why scientists might disagree about these data and their interpretations.